Rewrite ForceVariableDialog. It's not based on wx.TextEntryDialog

Don't customize standard wx.TextEntryDialog on the fly, implement your
own dialog for that with expected behavior and without any hacks.

merge updates to modbus/mb_runtime.c

fix 'SaveAs' in case of overwriting existing project

Traceback (most recent call last):
File "/home/developer/WorkData/PLC/beremiz/beremiz/BeremizIDE.py", line 959, in OnSaveProjectAsMenu
self.CTR.SaveProjectAs()
File "/home/developer/WorkData/PLC/beremiz/beremiz/ProjectController.py", line 600, in SaveProjectAs
self.SaveProject(old_project_path)
File "/home/developer/WorkData/PLC/beremiz/beremiz/ProjectController.py", line 579, in SaveProject
self._getProjectFilesPath(self.ProjectPath))
File "/usr/lib/python2.7/shutil.py", line 200, in copytree
os.makedirs(dst)
File "/usr/lib/python2.7/os.py", line 157, in makedirs
mkdir(name, mode)
OSError: [Errno 17] File exists: '/tmp/tests/project_files'

fix 'SaveAs' to non-empty directory and directory without write permissions

fix problems with recursive beremiz.h inclusion

remove LogMessage prototype from plc_main_head.c

it's not needed, because prototype is included in beremiz.h
But it caused problems with TARGET_LOGGING_DISABLE.

merge